Messages in this thread | | | Date | Sun, 30 Aug 2020 17:30:33 -0700 | From | "Darrick J. Wong" <> | Subject | Re: [PATCH] iomap: fix WARN_ON_ONCE() from unprivileged users |
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On Sat, Aug 29, 2020 at 09:30:57PM -0400, Qian Cai wrote: > It is trivial to trigger a WARN_ON_ONCE(1) in iomap_dio_actor() by > unprivileged users which would taint the kernel, or worse - panic if > panic_on_warn or panic_on_taint is set. Hence, just convert it to > pr_warn_ratelimited() to let users know their workloads are racing. > Thanks Dave Chinner for the initial analysis of the racing reproducers. > > Signed-off-by: Qian Cai <cai@lca.pw> > --- > fs/iomap/direct-io.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index c1aafb2ab990..6a6b4bc13269 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -389,7 +389,14 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length, > case IOMAP_INLINE: > return iomap_dio_inline_actor(inode, pos, length, dio, iomap); > default: > - WARN_ON_ONCE(1); > + /* > + * DIO is not serialised against mmap() access at all, and so > + * if the page_mkwrite occurs between the writeback and the > + * iomap_apply() call in the DIO path, then it will see the > + * DELALLOC block that the page-mkwrite allocated. > + */ > + pr_warn_ratelimited("page_mkwrite() is racing with DIO read (iomap->type = %u).\n", > + iomap->type);
Shouldn't we log the name of triggering process and the file path? Sort of like what dio_warn_stale_pagecache does?
--D
> return -EIO; > } > } > -- > 2.18.4 >
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